Answer:
hi there !!
B) Water evaporates into steam.
this is correct because only physical state changes, steam can be cooled down to get water again.
I'm not positive, but I believe it would be one near the Rocky Mountains.
The third answer is the one you want. You have to have an adjustable density. All other things being equal, if the tanks you use for holding just water when filled with water will let the sub sink, because the sub is made of a dense metal like iron or steel.
If on the other hand you fill these tanks with air, the net density will be below one and the sub will rise.